Vibratory reed signaling device



April 1953 v w. J. MULDOON 2,634,378

V I BRATORY REED SIGNALING DEVICE Original Filed Jan. 15, 1948 PatentedApr. 7, 1953 VIBRATORY REED SIGNALING DEVICE William J. Muldoon, GardenCity, N. Y., assignor to The Wheeler Insulated Wire Company,Incorporated, Bridgeport, Conn, a corporation of Delaware Originalapplication January 15, 1948, Serial No. 2,500. Divided and thisapplication July '7, 1950,

Serial No. 172,594

3 Claims.

The present invention relates to signaling devices. This application isa division of my copending application Serial No. 2,500, filed January15, 1948, now Patent No. 2,533,136, granted December 5, 1950.

In my copending application, Serial No. 570,585 filed May 17, 1946, nowPatent No. 2,523,775, granted September 26, 1950, I have described aninexpensive and efilcient sound powered transducer, which is especiallysuitable for toy telephones, inter-oiiice units, farm telephone systemsand the like. In my patent, No. 2,492,056 granted January 19, 1950, Ihave described a ringing unit for telephones of that general type. The.particular form of ringing units there described is especially designedfor use in a toy telephone and where only a small amount of power may berequired.

The object of the presentinvention is to provide a ringing unit of thegeneral type described in my last named copending application butarranged to provide a more powerful signal.

With this object in view and other objects as will hereinafter appear,the present invention comprises the various combinations andarrangements of parts hereinafter particularly described and claimed.

In the accompanying drawing, Fig. 1 is a side elevation of a signalingunit according to the present invention; Fig. 2 is a sectional elevationon line 22 of Fig. l; Sis an enlarged detail view of the receivingtransducer; Fig. 4 is an enlarged sectional view of line 44 of 1; Fig. 5is a. detail view of thereed release; and

Fig. 6 is a wiring diagram fora signaling system. In the illustratedembodiment of the invention, the complete set for one station comprisesa telephone handset (shown in the diagram of Fig. 6-) which may be ofany suitable form, and a casing 12 having an opening 13 into which theear piece of the handset may be received. The casing I2 encloses thebell and other parts of the ringing unit as will now be described.

Within the casing is a generator ringing unit comprising a vibratingreed l4, preferably in the form of a fiat resilient strip of metalanchored at one end in a bracket It. The reed I4 is coupled to thearmature ll of a transducer it. Also enclosed in the casing i2 is abell-ringing reed 23 adapted to be driven by a second transducer heredesignated as the receiving transducer. The

It comprises two permanent. magnets 24 and 25 in series in the magneticcircuit, with the armature 23 between them. Two pole pieces 26 and 28are secured to the magnets and their ends are closely adjacent to thearmature whereby small air gaps are formed. The armature is surroundedby a coil 30 which carries the signal current. The transducer shown inFig. 3 also includes means for biasing the armature, which is used onlyon the receiving unit and will be referred to later. Referring now tothe generating transducer, it has a winding 38 and its armature I! iscoupled with the reed l4 through a yoke 32. As shown in Fig. 4, the yokeis attached to the armature and it has a projecting portion with a slot42 within which the reed I4 is received. Preferably the reed is nottightly received in the slot but there is a slight looseness for reasonsto be explained later. It will be seen that upon vibration of the reedI4 the armature I1 is vibrated and a signal current at the frequency ofvibration is generated in the coil. It has been found that the bestresonant frequency is in the neighborhood of 60 cycles per second andfor this purpose the reed i preferably of spring steel having a freelength of about 5 inches, a width of and a thickness of .045". A weight36 may be mounted on the reed for a purpose to be described later.

Received within the casing is a bracket 38 which serves to mount thebell 40. Pivoted on the bracket 38 is a bell crank lever 42 having anarm 44 extending outwardly through the casing and carrying a manualoperating button 45. Upon depression of the button to carry the arm 44down through the slot 48 in the casing, the bell crank is rocked. Thearm 42 carries at the top a latching pawl 53 which extends over the reedH to exert a pulling motion thereon as shown in Fig. 5. The pawl ispivoted on a ledge 52 extending horizontally from the top of the bellcrank lever. The pawl is provided with a tail 54 which is adapted toengage a projection 55 extending outwardly from the bell mountingbracket 3% when the bell crank approaches the limit of its movement. Thepawl i normally held in its latching position by a wire spring 53. Acoil spring it connected between the bell crank and the mounting bracketnormally tends to hold the bell crank in its upward position. Upondepression of the button 45, the pawl 50 flexes the reed l 3 until thetall 54 of the pawl engages the projection 58 whereupon the pawl isturned to release the reed. The reed then undergoes a sharp powerfulseries of vibrations and causes generation of a signal voltage in thecoil through the vibration of the armature H.

The bell crank lever a2 is provided with a third arm 62 to operate aswitch 54 which will be described later. The switching arrangement issuch that the winding 30 of the generating unit at the transmittingstation is connected to the v V winding 3% of the receiving unit at thereceiving station, whereby the reed 28 of the receiving unit is vibratedsynchronously with the reed [4 of the transmitting unit.

It has been found that the ringing level is improved by permitting thereed I4 to store up energy for a portion of its vibrating cycle and thendischarge the energy rapidly into the magnetic system whereby a sharplypeaked wave form of voltage is obtained. This results in a highacceleration of the receiver reed by which the ringing is accomplishedat the receiving station. This result is accomplished by providing thesmall amount of looseness in the coupling 42 between the yoke 32 and thereed M, which has been previously referred to in connection with Fig. 4.

Referring now to the receiver unit, it is in general similar to thetransmitter unit heretofore described. The receiver unit includes thebell 0 and the vibratory reed 26, the latter being anchored as indicatedat 6B. The reed is formed at its upper end with a suitable bent portion68 entering within the bell and carrying a hammer E0.

The reed is operated by the transducer 22, which has already beenpartially described in connection with Fig. 3. It has been found thatgreater ringing force is obtained by biasing the receiver armature to apoint just short of that where the armature would strike one of the polepieces. The reason for this will be explained presently. The means forobtaining the bias is preferably as follows: An adjusting spring 86,which is a piece of fiat metal, is secured at one end to the pole piecesand at the other end to a block 88 through which passes an adjustmentscrew bearing on the armature 23. By turning the adjustment screw Bilthe required amount the armature can be biased toward one of the polepieces in any suitable degree.

The reason for the improved operation with the biased armature is thatthe force on the armature is proportional to the product and m, where5,. is the air gap flux due to the permanent magnets and ac is thealternating flux due to the signal current in the windings. When thearmature is biased toward one side, both s and {baa are increasedthrough one pole piece, and decreased through the other. A completeanalysis shows that the effect of the increased s due to greaterproximity to one pole piece considerably over balances the decreased 'sdue to the larger distance from the other pole piece.

It will be understood that a sufiicient overall air gap must always beprovided to take care of minimum economical tolerances and to insureagainst large performance variations and critical adjustment of thearmature in the gap. The biasing of the armature as herein describedshortens one of the air gaps and the resultant effect is not unlike whatwould be obtained if the unit were originally constructed with air gapsof the diminished amount on both sides of the armature. However, itwould be difiicult to construct such a unit and to adjust the armaturefor optimum performance. The biasing arrangement herein shown allows thearmature to be adjusted to the optimum setting; in other words, for agiven overall air gap, a maximum ringing force is obtained by biasingthe armature toward one side.

Another feature of importance is that of using a relatively massivevibrating element for the generator and a relatively light one for thereceiver. Thus the generating reed has the weight 35, which contributesto the mass of the vibrating system, while the mass of the receivingsystem is preferably less. Since the vibrating systems of the generatorand receiver are to resonate at the same frequency, this requires thatthe elastance of generating reed it be greater than that of thereceiving reed 2G; in other words, the reed I4 is necessarily stifferthan the read Zil. In such a case the energy is approximatelyproportional to the mass; accordingly, the generating reed can store alarge amount of energy, While the receiving reed does not withdraw muchenergy from the system. Thus both reeds can vibrate for a longer timethan if they were of the same characteristics.

The preferred wiring diagram is shown in Fig. 6. The switch 64 which isoperated by the arm 62 of the bell crank has a movable contact normallyclosed on a fixed contact 9 3 which is connected in series with themovable contact 96 of a hook switch. The contact 92 is adapted to closeon a contact 97 when the button 46 is depressed. The contact 96 isclosed on a contact 88 when the handset 99 is supported by the easing l2and is adapted to close on the contact its when the handset is removed.One line H32 is connected to the windings 30 and 3B and to the handset.The other ends of the windings 3B and 3B are connected to the contacts98 and 91 respectively. The contact [G0 is connected with the handsetand the contact 92 is connected with the line I06.

Upon depression of the button 66, the generator winding 38' is connectedto the line by reason of the closure of contact 92 on 9?. Contacts $2and 91 remain closed during the vibration of the reed [4. At thereceiving end, however, the winding 30 is connected to the line throughcontacts 98, 95 and 94, 92. The proper'windings of the two units arethus connected together, whereby the bell is caused to ring at thereceiving station by reason of vibration of the reed 20. Upon lifting ofthe handsets 99 at both ends, both hook switches are closed at 96, I60,and since contact 92 is then closed on 95, the handsets are connectedtogether through the lines for ordinary telephonic conversation.

It will be seen that the construction is in gen.- eral similar to thatused in the ringing device described in Patent No. 2,492,056. However,it difiers in some respects. Among other things, it has been founddesirable to use separate transmitting and receiving units since bothcan be then constructed for maximum ringing en: ergy, as heretoforedescribed. With the apparatus herein described, it has been foundpossible to obtain a substantial volume of ringing with only the energythat can be introduced by operation of the button 46. As heretoforestated, the unit is particularly suitable for point-to-pointcommunication in batteryless systems and is found particularly useful infarm units where house-to-barn or house-to-field communication isdesired.

I claim:

1. A transducer comprising two permanent magnets in series, an armaturesecured at one end between the magnets, pole pieces extending fromopposite ends of the magnets into proximity with the free end of thearmature to form an air gap between the armature and the tip of eachpole piece, a coil wound about the armature, and spring means forbiasing the armature toward one or the pole pieces to cause it tovibrate about an axis which is relatively nearer one of the pole pieces.

2. A transducer comprising two permanent magnets in series, an armaturesecured at one end between the magnets, pole pieces extending fromopposite ends of the magnets into proximity with the free end of thearmature to form an air gap between the armature and the tip of eachpole piece, a coil Wound about the armature, and means for biasing thearmature toward one of the pole pieces, said means comprising a springmember, and a screw carried by the spring member and bearing against thearmature to cause it to vibrate about an axis which is relatively nearerone of the pole pieces.

3. A transducer comprising two permanent magnets in series, an armaturesecured at one end between the magnets, pole pieces extending fromopposite ends of the magnets into proximity with the free end of thearmature to form an air gap between the armature and the tip of eachpole piece, the armature extending outwardly beyond the pole pieces,acoil surrounding the armature, and means for biasing the armaturetoward one of the pole pieces, said means including a leaf springoverlying the outwardly extending portion of the armature, and aconnection between said spring and the armature, to cause it to vibrateabout an axis which is relatively nearer one of the pole pieces.

WILLIAM J. MULDOON.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,306,068 Lewis Dec. 22, 19422,328,831 Mendelson Sept. 7, 1943 2,433,740 Collins Dec. 30, 1947

